Waterfoil



@cto E934 Q. TEETJENS 3 9 WATERFOIL Original Filed'Nov, 6, 1951 2Sheets-Sheet 1' ATTOR N EYS.

Oct 9, 1934.

O. G. TIETJENS WATERFOIL Original Fil ed Nov. 6, 1931 2 Sheets-Sheet 2ascarafi ijems Patented Oct. 9, 1934 UNITED STATES PATENT OFFICEApplication November 6, 1931, Serial'No. 573,459 Renewed December 14,1933 7 Claims.

This invention relates to hydrocrafts and more particularly tohydro-foils especially adapted to decrease resistance between a craftand the water for the purpose of permitting excessive speeds to beobtained with an expenditure of a minimum amount of motive power andsaid device is capable of lifting the'hull of the craft further andfurther out of the water as the speed increases until the hull isentirely clear of the surface of the water so that water resistance willbe reduced to a minimum.

Another object of this invention is the provision of hydrofoils soshaped and constructed that they willbe capable of producing maximum ulifting forces with minimum contact with the water and which are capableof producing their greatest lifting forces when the hull of the craft iswithin the water to assure quick and easy rise of the hull of the craftfrom the water as the a speed thereof increases.

A further object of this invention is the provision of hydrofoils whichalways terminate above the surface of the water when the hull of thehydrccraft is travelling at high speeds and which are so constructed asto counteract any tendency of the hull to turn about its longitudinalaxis due to some foreign force acting thereon while supported clear ofthe water thus increasing the stability of the device to a maximum.

With these and other objects in view, this invention consists in certainnovel features of construction, combination and arrangement of parts tobe hereinafter more fully described and claimed. 7

For a complete understanding of my invention, reference is to be had tothe following description and accompanying drawings, in which Figure 1is a side elevation illustrating a hull of a water craft with hydrofoilsattached thereto and constructed in accordance with my invention andshowing the hull resting within the water.

Figure 2 is a view similar to Figure 1 illustrating the hull of thecraft supported clear of the surface of the water by the hydrofoils andin a position occupied while travelling at excessive speed.

Figure 3 is an end elevation illustrating the hull of the craft restingwithin the water.

Figure iris a view similar to Figure 3 showing the hull supported abovethe surface of the water.

, the line 55 of Figure 1 illustrating means for varying the incidenceof the rearhydrofoil.

Figure 6 is a diagrammatical view illustrating the lines of forcecreated by the hydrofoil should Figure 5 is a detail sectional viewtaken onthe hull of the craft tilt or turn about its longi- V tudinalaxis.

Figure 7 is a diagrammatical view showing the hull tilted in a clockwisedirection by a foreign force.

Figure 8 is a similar view showing the hull tilted in a counterclockwisedirection by a foreign force.

Figure 9 is an end elevation illustrating a modifi-edform of myinvention wherein the hydrofoil comprises angularly related portions.

Figure 10 is a view similar to Figure 9 showing another modified form ofmy invention.

Figure 11 is a sectional view taken on the line 11-11 of Figure 3.

Figure 12 is a sectional view taken on the line l212 of Figure 3.

Figure 13 is a sectional view illustrating a modified form of upperstructure to the hydrofoil.

Referring in detail to the drawings, the numeral 1 indicates the hull ofa watercraft to which hydrofoils 2 are secured and it is to beunderstood that two or more hydrofoils may be successfullyemployed onthe hull of a craft and the number of hydrofoils are preferablyincreased in accordance with the increase in lengths of different hulls.However, I have found that a hydrofoil such as 2 is capable in itself ofgiving the required lift as well as maintaining the desired stabilityabout the longitudinal axis of smaller hulls. The hull shown in Figures1 and 2 is of the size or length usually employed in watercraftsespecially adapted for high speeds and a hull of this size hashydrofoils secured thereto adjacent its bowand stern as shown in thedraw-. ings. The rear hydrofoil is shown as pivotally connected tothehull and is provided with an operating medium whereby the incidence ofthe respective hydrofoil may be varied, however, the rear hydrofoil maybe fixed to the hull similar to the connecting. of the front hydrofoilto the hull.

Each hydrofoil includes a lower plane element 4 which is arrangedtransversely and below the bottom of the hull and has formed integralwith its ends upper plane elements 5 that extend inwardly and upwardlytoward the sides of the hull and are suitably secured thereto. The planeelement 4 is of any suitable shape in cross section and preferably asshown in Figure 11 and the upper plane elements 5 are preferably of anincreased thickness over the element 4 and may be of any desired shape,preferably as shown in Figure 12 or if desired, the cross sectionalshape of the elements 5 may be as shown in Figure 13, frequently termedtear shape. The purpose of conabout a righting of the hull.

structing or designing the upper plane elements 5 of greater thicknessthan the lower element 4 is to provide the greatest lifting force to thehull when the latter is resting within the water, it being understoodthat the upper plane elements 5 create lifting forces in an upwarddirection along with the lifting forces produced by the lower planeelement 4 as the hull begins to move forwardly in the water. As thespeed of the hull increases the hydrofoils lift it more and more out ofthe water until the hull is clear of the water and assumes a positionsubstantially as shown in Figure 2 and when in the latter namedposition, the water resistance to the craft is reduced to a minimum.With the hull travelling in a position as shown in Figure 2 it isdesirable as the speed increases to cause the bow of the hull to moveslightly in a downward direction and in order to accomplish this therear foil may be adjusted slightly to vary its incidence of attack onthe water.

The center line of the hull 1 is indicated by the line E-E and thelongitudinal axis through the center of gravity of the hull is indicatedat A.

The radius of curvature of the lower plane element 4 is greater than thedistance between said element 4 and the longitudinal axis A so that thelifting forces created by the foil will cross the center line E-E of thehull at points above the dinal axis in a clockwise direction and thehydrofoil assume the position indicated by the line C, the lifting forceof the lower element of said hydrofoil will be upwardly and across thecenter line EE above the longitudinal axis A as shown 'at P which forcecounteracts the forces having a tendency to turn the hull in the stateddirection about the longitudinal axis and thereby bring Should the hulldue to'a foreign force have a tendency to rotate about its longitudinalaxis in a counterclockwise direction and assume the position indicatedby the line B in Figure 6 the force of the lower element of thehydrofoil counteracts the tendency of the hull to turn in acounterclockwise direction by [crossing the center line E-E of the'hullabove the longitudinal axis A. It is understood that only the immersedparts of the hydrofoils create the lifting forces. The hull when tiltedby a foreign force about its longitudinal axis, the upper porforce andovercomes the latter to aid in righting the hull.

Thus it will be seen that the hydrofoils besides efficiently raising thehull out of the water as the speed increases they also will efficientlystabilize the hull which is extremely desirable I when travelling atexcessive speeds.

In order to obtain stability of watercrafts of the foregoing describedtype it is essential that the hydrofoils be so arranged that there willbe L a restoring moment if the hull is given a slight angular rotationor turn about its longitudinal axis.

Referring to my modified form of invention as shown in Figure 9, thehydrofoil includes a lower plane element 6 and upper plane elements 7sim-' ilar in construction to the upper plane elements 5. The lowerplane element 6 includes portions 8, 9 and 10, the portion 8 beingdisposed substantially straight and arranged transversely of the hulland below the bottom thereof, with the portions 9 and 10 disposedangularly thereto and inclining upwardly and outwardly therefrom andformed integralwith the outer ends of the portions '7. The hydrofoil 6constructed in accordance with the foregoing will have approximately thesame lifting ability as the hydrofoil shown in Figures 3 and a and alsoapproximately the same stability. Referring to stability andparticularly to Fig. 9, it will be noted that, in a manner similar tothat shown in Fig. 6, the immersed parts of the portions 8, 9, and 10are disposed substantially in the arc of a circle M, the center of theare being located at P, beyond the axis A. Also, that the immersed parts8, 9, and 10 exert forces a: which are normal thereto and whichintersect at P Referring to Figure 10 wherein another modified form ofmy invention is disclosed the hydrofoil 11 includes the lower planeelement 12 similar in construction to the lower plane element 4 and5100.

merges into the upper plane elements 13 by arcuately curved end portions14.

While I have shown and described the preferred embodiment of myinvention, it will be understood that minor changes in construction,combination and arrangement of parts may be made without departing fromthe spirit and scope of my invention, as claimed.

Having thus described my invention, what I claim is:

1. A hydrofoil comprising an element arranged below and transversely ofthe hull of a watercraft and secured to the hull, said element includinglower and upper portions forming planes to produce a lifting force tothe hull for elevat- I ing the latter outwardly of the water as thespeed thereof increases, said lower portion being arcuately curved andthe radius of curvature of said lower portion being greater than thedistance between said lower portion and the longitudinal 5x20 axis ofthe hull, said lifting force passing by the longitudinal axis of thehull at the right side when some foreign force turns the hull in aclockwise direction about its longitudinal axis, and said lifting forcepassing by the longitudinal axis of C the hull at the left side when aforeign force turns the hull about a longitudinal axis in an oppositedirection.

2. A hydrofoil comprising a lower curved portion, upper portionsextending from the ends of,v the lower portion and arranged at an anglethere to and secured to a hull of a water craft, the radius of curvatureof said lower portion being greater than the distance between the lowerportion and the longitudinal axis of the hull to produce a lifting forceto the hull which extends through the center line of the hull above thelongitudinal axis of said hull when a foreign force acts to turn thehull about its longitudinal axis.

3. A hydrofoil comprising an element arranged below and extendingtransversely of the hull of a watercraft and secured to said hull, saidelement including lower and upper portions forming planes to produce alifting force to the hull for lifting the latter outwardly of the wateras, the speed thereof increases, said lower portion consisting ofangularly related connected portions, the immersed part of which, forany normal position of the watercraft lies substantially in a circle,the center of said circle being located above the longitudinal axiswhich passes through the center of gravity of the watercraft.

4. A hydrofoil for a watercraft comprising an element disposed below andextending transversely of the hull of the watercraft and secured to saidhull, said hydrofoil including lower and upper longitudinally extendingsustaining planes whereby the hull is lifted outwardly from the water bythe speed of the craft, said lower planes having an immersed portionwhich for any normal position of the craft lies substantially in a.circle the radial center of which is located above the longitudinal axiswhich passes through the center of gravity of the watercraft.

5. A hydrofoil for a watercraft comprising an element disposed below andextending transversely of the hull of the watercraft and secured to saidhull for lifting the hull outwardly of the water by the speed of thecraft, said hydrofoil having an immersed portion which for any normalposition of the craft lies substantially in a circle the radial centerof which is located above the longitudinal axis which passes through thecenter of gravity of the watercraft.

6. A hydrofoil for a watercraft, comprising a sustaining plane disposedbelow and extending transversely of the hull of the watercraft andsecured to said hull, whereby the hull is lifted outwardly from thewater by the speed of the craft, said sustaining plane having animmersed portion which, for any normal position of the craft, liessubstantially in a circle, the radial center of which is located abovethe longitudinal axis which passes through the center of gravity of thewatercraft.

7. A hydrofoil for a watercraft, comprising a member disposed below andextending transversely of the hull of the watercraft and of suchlongitudinal cross-section as to lift the hull outwardly of the water bythe speed of the craft, said lifting member including angularlyconnected elements, the immersed portions of said elements exerting, forany normal position of the craft, lifting forces substantiallyperpendicular to the immersed portions and in directions which intersectbeyond the longitudinal axis of the hull.

OSCAR G. TIETJENS.

